The present invention relates generally to the field of communication systems, and more particularly, to an apparatus and method for implementing a reduced slotted mode in a communication system.
Call setup for a mobile station terminated call can take several seconds or more to complete. Although this length of time may be acceptable for voice calls, it has a significant negative impact on the user""s perception of call quality for data calls. Therefore, in typical deployments, the traffic channel is maintained during a period of data inactivity before the data call is released to the dormant state. Such prolonged maintenance of the data call during periods of data inactivity results in inefficient use of RF and channel element resources. The desirable reduction or elimination of hold over time, while preserving acceptable service for the end user, requires fast call setup time.
One of the most significant components of call setup for mobile station terminated calls is the paging delay. While in the Idle State, the mobile station typically operates in the Slotted Mode in order to conserve battery life. In the Slotted Mode, the mobile station monitors the forward common control channel for pages only during certain assigned time slots. The Slot Cycle Index (SCI) governs how often the mobile station checks for a page. The lowest currently standardized SCI value (i.e. 0) corresponds to 1.28 seconds. Thus, a page for a mobile station using the shortest slot cycle in the Slotted Mode can be delayed up to 1.28 seconds, even when the lowest SCI value is used.
As previously described, the cdma2000 standard currently supports the concept of Slotted Mode. Slotted Mode is described in the TIA/EIA IS-2000.5 standard, section 2.6.2.1.1.3. However, Slotted Mode as currently defined has a significant impact to call setup delay because the shortest slot cycle is 1.28 seconds. The cdma2000 standard also currently supports a Slotted Timer feature. In accordance with this feature, the mobile station operates in Non-Slotted Mode, i.e., continuously monitors the forward common control channel, following its release from the traffic channel for a duration of time specified by the Slotted Timer (provided by the base station). A significant drawback to this feature is that continuously monitoring the forward common control channel has a significant impact on the battery life of the mobile station. Also, the feature is controlled entirely by the base station. The mobile station is unable to request being put in Non-Slotted Mode.
One proposed solution that has been introduced for standards body consideration is to allow reduced SCI values. If accepted, the proposal would reduce the shortest slot cycle down to 80 ms. However, under the solution, the only way for a mobile station to change its SCI is via mobile registration. Therefore, in order to effectively make use of the reduced SCI without wasting mobile station battery life, the mobile station must register each time it changes between a reduced SCI value (i.e. while a packet data session is dormant) and a higher SCI value (i.e. while there is no dormant packet data session). This results in increased loading on the air and IOS interfaces.
Thus, a need exists for an apparatus and method for implementing a reduced slotted mode, with minimal impact on the air and IOS interfaces.